Display device and touch sensing method thereof

ABSTRACT

In a display device, a driving element is disposed on a rear substrate, and a passivation layer covers the driving element. A pixel electrode is disposed on the passivation layer and is connected to the driving element. An organic emission layer is disposed on the pixel electrode and is configured to emit tight toward the rear substrate. A common electrode is disposed on the organic emission layer. A touch electrode is disposed between the rear substrate and the passivation layer, and it forms a capacitive component when an external touch occurs.

RELATED APPLICATIONS

This application claims priority to and the benefit of Korean PatentApplication No. 10-2015-0013040 filed in the Korean IntellectualProperty Office on Jan. 27, 2015, the entire contents of which areincorporated herein by reference.

BACKGROUND

(a) Field

The described technology relates generally to a display device and atouch sensing method thereof, and particularly relates to an organiclight emitting device having a touch sensing function and a touchsensing method thereof.

(b). Description of the Related Art

Among display devices, since an organic light emitting diode (OLED)display as a self-light emitting type that does not require a separatelight source, it is advantageous in terms of power consumption, responsespeed, viewing angle, and contrast ratio.

The organic light emitting diode (OLED) display includes a plurality ofpixels such as red pixels, blue pixels, green pixels, and white pixels,and may express full colors by combining the pixels. Each pixel includesa light emitting element, and a plurality of thin film transistors fordriving the light emitting element.

The light emitting element of the organic light emitting diode (OLED)display includes a pixel electrode, a common electrode, and an emissionlayer positioned between the two electrodes. One of the pixel electrodeand the common electrode becomes an anode and the other becomes acathode. Electrons injected from the cathode and holes injected from theanode are coupled with each other in the light emitting layer to formexcitons, and the excitons emit light while discharging energy. Thecommon electrode is formed throughout a plurality of pixels to transmita predetermined common voltage.

The OLED display may be divided into a bottom emission type in whichlight is emitted to the bottom of a substrate and a top emission type inwhich light is emitted to the top of the substrate. In the case of thetop emission type of OLED display, the common electrode may be made of atransparent conductive material.

On the other hand, recently, a display device having a function ofsensing external touch of a finger, etc., of a person has been activelydeveloped. The external touch sensing function means a function in whichit is capable of sensing touch information such as a touch existence anda touch position when an external object such as the finger or a touchpen approaches or contacts a screen. This function may allow a machinesuch as a computer, etc., to perform a desired command by touching afinger or a touch pen (or stylus) to a screen of the touch panel towrite or draw characters or execute icons.

In this instance, a glass substrate for a touch may be formed on asubstrate to provide the touch sensing function to the bottom emissiontype of organic light emitting device. However, the organic lightemitting device becomes thicker and heavier because of the glasssubstrate used for a touch.

SUMMARY

Embodiments provide a display device having a touch sensing function,and a touch sensing method thereof.

An embodiment provides a display device including a rear substrate, adriving element disposed on the rear substrate, a passivation layercovering the driving element, a pixel electrode disposed on thepassivation layer and connected to the driving element, an organicemission layer disposed on the pixel electrode and configured to emitlight toward the rear substrate, a common electrode disposed on theorganic emission layer, and a touch electrode disposed between the rearsubstrate and the passivation layer and configured to form a capacitancecomponent when a touch is generated.

The touch electrode may be connected to the pixel electrode.

The display device may further include a buffer layer disposed betweenthe rear substrate and the driving element. The touch electrode may bedisposed between the rear substrate and the buffer layer.

The touch electrode may cover the organic emission layer and include atransparent conductive material.

The touch electrode may expose the organic emission layer and include areflective conductive material.

The touch electrode may be disposed on a same layer as a semiconductorlayer of the driving element and include a semiconductor material.

The display device may further include a sensing element disposed on asame layer as the driving element and configured to transmit a sensingsignal for sensing a touch. The touch electrode may be connected to thesensing element.

The display device may further include an auxiliary electrode disposedon a same layer as the pixel electrode and separated from the pixelelectrode. The auxiliary electrode may be connected to the touchelectrode.

The driving element may include a first gate electrode and a second gateelectrode disposed on the first gate electrode, and the touch electrodemay be disposed on a same layer as the first gate electrode.

The touch electrode may include a transparent conductive material.

Another embodiment provides a display device including at least onesignal line configured to transmit a data signal and a sensing signal, ascan line configured to transmit a scan signal, a pixel, and sensingsignal processor. The pixel includes a touch electrode for storing avoltage corresponding to the sensing signal for a first period when anexternal touch occurs, and is disposed in a region defined by the signalline and the scan line. The sensing signal processor is configured tomeasure a voltage stored in the touch electrode through the signal linefor a second period after the first period, measure a voltage of thesignal line for a third period after the second period, and sense theexternal touch based upon a difference between the voltage measured forthe second period and the voltage measured for the third period.

The pixel may further include a switching transistor configured totransmit the data signal in response to the scan signal, a capacitorconfigured to store a voltage corresponding to the data signal from theswitching transistor, a driving transistor configured to output acurrent caused by the voltage stored in the capacitor, and an organiclight emitting element configured to emit light according to the currentfrom the driving transistor.

The touch electrode may be connected to a first terminal of the organiclight emitting element.

The touch electrode may be connected to a gate electrode of the drivingtransistor.

The display device may further include a sensing transistor. The sensingtransistor may be configured to be turned on for the first period totransmit a voltage stored in the touch electrode to the signal line.

The sensing transistor may include a first input/output terminalconnected to the signal line and a second input/output terminalconnected to the touch electrode.

The signal line may include a data tine configured to transmit the datasignal and a sensing line configured to transmit the sensing signal.

The signal line may include a data line configured to transmit the datasignal for a displaying period and to transmit the sensing signal for atouch sensing period.

The touch sensing period may include the first period, the secondperiod, and the third period.

The sensing signal processor may include an operational amplifierincluding a first input terminal connected to the signal line, a secondinput terminal configured to receive a reference voltage, and an outputterminal, a first capacitor, a second capacitor, a first switchingelement connected between the output terminal and the first capacitorand configured to be turned on for the second period, and a secondswitching element connected between the output terminal and the secondcapacitor and configured to be turned on for the third period.

Another embodiment provides a touch sensing method by a display deviceincluding at least one signal line for transmitting a data signal and asensing signal, a scan line for transmitting a scan signal, and a pixeldisposed in a region defined by the signal line and the scan line andincluding a touch electrode.

The touch sensing method includes storing a voltage corresponding to thesensing signal in the touch electrode for a first period when anexternal touch is generated, measuring the voltage stored in the touchelectrode through the signal line for a second period after the firstperiod, measuring the voltage at the signal tine for a third periodafter the second period, and sensing the external touch based upon adifference between the voltage measured for the second period and thevoltage measured for the third period.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of an organic light emitting deviceaccording to an embodiment.

FIG. 2 shows an equivalent circuit diagram of one pixel of an organiclight emitting device according to an embodiment.

FIG. 3 shows one frame of an organic light emitting device according toan embodiment.

FIG. 4 shows a block diagram of a sensing signal processor of a displaydevice according to an embodiment.

FIG. 5 shows a connection relationship between a sensor and a pixel in adisplay device according to an embodiment.

FIG. 6 shows signal timing during a sensing period in an organic lightemitting device according to an embodiment.

FIG. 7, FIG. 9, FIG. 10, FIG. 11, FIG. 12, FIG. 13, and FIG. 14 areequivalent circuit diagrams of one pixel of an organic light emittingdevice according to various embodiments.

FIG. 8 shows signal timing during a sensing period in an organic lightemitting device including one pixel shown in FIG. 7.

FIG. 15 shows one frame of an organic light emitting device according toanother embodiment.

FIG. 16 and FIG. 17 show equivalent circuit diagrams of a sensing regionof an organic light emitting device according to various embodiments.

FIG. 18 and FIG. 19 show cross-sectional views of an example of onepixel of an organic light emitting device shown in FIG. 2.

FIG. 20 shows a cross-sectional view of an example of one pixel of anorganic light emitting device shown in FIG. 7.

FIG. 21 shows a cross-sectional view of an example of one pixel of anorganic light emitting device shown in FIG. 9.

FIG. 22 shows a cross-sectional view of an example of one pixel of anorganic light emitting device shown in FIG. 10.

FIG. 23 and FIG. 24 show cross-sectional views of another example of onepixel of an organic light emitting device shown in FIG. 7.

FIG. 25 shows a cross-sectional view of another example of one pixel ofan organic light emitting device shown in FIG. 2.

DETAILED DESCRIPTION

In the following detailed description, only certain embodiments havebeen shown and described, simply by way of illustration. As thoseskilled in the art would realize, the described embodiments may bemodified in various different ways, all without departing from thespirit or scope of the inventive concept. Accordingly, the drawings anddescription are to be regarded as illustrative in nature and notrestrictive. Like reference numerals designate like elements throughoutthe specification.

FIG. 1 shows a block diagram of an organic light emitting deviceaccording to an embodiment, FIG. 2 shows an equivalent circuit diagramof one pixel of an organic light emitting device according to anembodiment, and FIG. 3 shows one frame of an organic light emittingdevice according to an embodiment.

Referring to FIG. 1, the organic light emitting device includes adisplay panel 300, a scan driver 400, a data driver 500, a sensing scandriver 600, a sensing signal processor 700, and a signal controller 800.

Referring to FIG. 1, the display panel 300 includes a plurality ofsignal lines S1-Sn D1-Dm and SE1-SEn and a plurality of pixels PXconnected thereto and arranged substantially in a matrix form.

The signal lines S1-Sn D1-Dm and SE1-SEn include a plurality of scantines S1-Sn for transmitting a scan signal, a plurality of data linesD1-Dm for transmitting a data signal according to an input image signal,and a plurality of sensing signal tines SE1-SEn for transmitting a scansignal for sensing a touch. The scan tines S1-Sn extend substantially ina row direction and are substantially parallel with each other, and thedata lines D1-Dm extend substantially in a column direction and aresubstantially parallel with each other. A plurality of pixels PX arerespectively formed in regions defined by the scan lines S1-Sn and thedata lines D1-Dm.

The sensing signal lines SE1-SEn extend substantially in the rowdirection, are substantially parallel with each other, and are connectedto the pixel PX of the corresponding row. In an embodiment, one sensingsignal line may be connected to a pixel bunch of a plurality of rows. Inthis case, the pixel bunch defined by a plurality of rows correspondingto one sensing signal line and at least one column may define a sensingregion.

In an embodiment, the signal lines may further include a plurality ofsensing lines (not shown) for transmitting a sensing signal. The sensinglines extend substantially in the column direction, are substantiallyparallel with each other, and are connected to the pixels PX of thecorresponding columns In an embodiment, one sensing line may beconnected to a pixel bunch of a plurality of columns. In this case, thepixel bunch defined by at least one row and a plurality of columnscorresponding to one sensing line may define a sensing region.

In an embodiment, a pixel bunch defined by a plurality of rowscorresponding to one sensing signal line and a plurality of columnscorresponding to one data line or one sensing line may define a sensingregion.

The scan driver 400 is connected to the scan lines S1-Sn of the displaypanel 300, and applies a scan signal that is a combination of a voltagewith a level for turning on a switching transistor of the pixel PX and avoltage with a level for turning it off to the scan lines S1-Sn.

The data driver 500 is connected to the data lines D1-Dm of the displaypanel 300, and applies a data voltage to the data lines D1-Dm. The datadriver 500 may select a data voltage from among all gray voltagesrelating to luminance of a pixel PX, or may divide gray voltages of alimited number to generate a desired data voltage.

The sensing scan driver 600 is connected to the sensing scan lines(SE1-SEn) of the display panel 300, and applies a sensing scan signalthat is a combination of the voltage for turning on the switchingtransistor of the pixel PX and the voltage for turning it off to thesensing scan lines SE1-SEn.

The sensing signal processor 700 is connected to the data lines D1-Dm,and senses a sensing state in the sensing region defined by the sensingscan line for transmitting the corresponding sensing scan signal and thecorresponding data line through the signal that is transmitted throughthe data lines D1-Dm according to the sensing scan signal, in anembodiment, the sensing signal processor 700 is connected to a sensingline (not shown) to sense a sensing state in the sensing region definedby the sensing scan line and the sensing line according to the signaltransmitted through the sensing line.

The signal controller 800 controls the scan driver 400, the data driver500, the sensing scan driver 600, and the sensing signal processor 700.

The driving devices 400, 500, 600, 700, and 800 may be directly mountedas at least one single IC chip on the display panel 300, may be mountedon a flexible printed circuit film (not shown) and be attached as a tapecarrier package (TCP) to the display panel 300, or may be mounted on anadditional printed circuit board (PCB) (not shown). Differing from this,the driving devices 400, 500, 600, 700 and 800 may be integrated on thedisplay panel 300 together with the signal lines D1-Dm, and SE1-SEn andswitching transistors. Further, the driving devices 400, 500, 600, 700,and 800 may be integrated into a single chip, and in this case, at leastone of them or at least one circuit element configuring them may beprovided outside the single chip.

Referring to FIG. 2, for example, the pixel PX connected to the i-th(i=1, 2, . . . , n) scan line Si and the j-th (j=1, 2, . . . , m) dataline Di includes a switching transistor Qs, a driving transistor Qd, asensing transistor , a storage capacitor Cst, and an organic lightemitting element LD.

The switching transistor Os includes a control terminal connected to thescan line Si, a first input/output terminal connected to the data lineDj, and a second input/output terminal connected to a control terminalof the driving transistor Qd. The switching transistor Qs transmits thedata signal provided through the data line Di to the driving transistorQd in response to the scan signal provided through the scan line Si.

The driving transistor Qd includes a control terminal connected to thesecond input/output terminal of the switching transistor Qs, a firstinput/output terminal connected to a driving voltage line (ELVDD), and asecond input/output terminal connected to the organic light emittingelement LD. The driving transistor Qd outputs an output current that isvariable by a voltage between the control terminal and the secondinput/output terminal.

The capacitor Cst is connected between the control terminal of thedriving transistor Qd and the first input/output terminal. The capacitorCst charges the data signal applied to the control terminal of thedriving transistor Qd and maintains the same when the switchingtransistor Qs is turned off.

The organic light emitting element LD tray exemplarily be an organiclight emitting diode (OLED), and may include an anode connected to thesecond input/output terminal of the driving transistor Qd and a cathodeconnected to the common voltage ELVSS. The organic light emittingelement LD displays an image by differentiating intensity according toan output current of the driving transistor (Qd) and emitting light. Theorganic light emitting element LD may include an organic material forproperly emitting one or at least one of primary colors (i.e., red,green, and blue) or may include an organic material for emitting white,and the organic light emitting device may display the desired image witha spatial sum of the colors.

The sensing transistor e includes a control terminal connected to thesensing scan line SEi, a first input/output terminal connected to thedata line Dj and a second input/output terminal connected to the anodeof the organic light emitting element LD. The sensing transistor Qstransmits the voltage at the anode of the organic light emitting elementLD to the data line Dj in response to the sensing control signalprovided through the sensing scan tine SEi.

A touch electrode (not shown) is connected to the anode of the organiclight emitting element LD, and the touch electrode forms a touch sensingcapacitor Cto with an external touch on a rear substrate as anotherelectrode. In one embodiment, the touch electrode may include aconductive material. In another embodiment, the touch electrode mayinclude a semiconductor material. Here, a buffer layer (not shown)formed between the anode and the rear substrate may function as adielectric layer. The touch sensing capacitor Cto charges the sensingsignal applied to the anode of the organic light emitting element LD.

The switching transistor Qs, the driving transistor Qd and the sensingtransistor Qe are p-channel electric field effect transistors (FETs),but at least one of them may be an n-channel electric field effecttransistor, In this case, the control terminal is a gate electrode, oneof the first input/output terminal and the second input/output terminalis a source electrode, and the other thereof is a drain electrode,Further, connections among the transistors Qs, Qd, and Qe, the capacitorCst, and the organic light emitting element LD may be changed.

Referring to FIG. 3, one frame is divided into a displaying period forthe organic light emitting device to perform a displaying operation anda touch sensing period for the organic light emitting device to sense atouch. During the displaying period, low-level scan signals SCAN1-SCANnare sequentially applied to a plurality of scan lines S1-Sn, and a datasignal is applied to a plurality of data lines D1-Dm while the low-levelscan signals SCAN1-SCANn are applied. During the touch sensing period,low-level sensing scan signals SCAN_SEN1-SCAN_SENn are sequentiallyapplied to a plurality of sensing scan lines SEN1-SENn and a sensingsignal is applied to a plurality of data lines D1-Dm while the low-levelsensing scan signals SCAN_SEN1-SCAN_SENn are applied. Accordingly, theorganic light emitting device may perform the display operation basedupon the data signal for the displaying period and may perform the touchsensing operation based upon the sensing signal for the touch sensingperiod.

FIG. 4 shows a block diagram of a sensing signal processor of a displaydevice according to an embodiment, and FIG. 5 shows a connectionrelationship between a sensor and a pixel in a display device accordingto an embodiment FIG. 5 shows a case in which a sensor 710 is connectedto one data line Dj and one pixel PX is connected to the data line Dj.

Referring to FIG. 4, the sensing signal processor 700 includes aplurality of sensors 710 each of which is connected to at least onecorresponding data line.

Referring to FIG. 5, the sensor 710 includes an operational amplifier711, capacitors Cs1 and Cs2, and switching elements SE, RST, CD1, andCD2.

A reference voltage Vset is applied to a first input terminal of theoperational amplifier 711.

The switching element SE is connected between a second input terminal ofthe operational amplifier 711 and a corresponding data line Dj. Theswitching element SE is turned on in response to a switching controlsignal SSE, and transmits a voltage of the data line Dj to the secondinput terminal of the operational amplifier 711 for the sensing periodfor performing a touch sensing operation in the organic light emittingdevice.

The switching element RST is connected between the second input terminaland an output terminal of the operational amplifier 711, and is turnedon in response to a switching control SRST to allow the operationalamplifier 711 to function as a unit gain operational amplifier, that is,a buffer.

The switching element CD1 is connected between the output terminal ofthe operational amplifier 711 and a first terminal of the capacitor Cs1and a second terminal of the capacitor Cs1 is connected to apredetermined power terminal, such as a ground. The switching elementCD1 charges an output voltage of the operational amplifier 711 into thecapacitor Cs1 in response to a switching control signal SCD1.

The switching element CD2 is connected between the output terminal ofthe operational amplifier 711 and the first terminal of the capacitorCs2, and a second terminal of the capacitor Cs2 is connected to apredetermined power terminal, such as the ground. The switching elementCD2 charges the output voltage of the operational amplifier 711 into thecapacitor Cs2 in response to the switching control signal SCD2.

The sensor 710 determines a touching state based upon a differencebetween the voltages charged in the capacitors Cs1 and Cs2.

A switching element DE may be connected between the data driver 500 andthe data line Dj. The switching element DE is turned on in response to aswitching control signal SDE, and transmits the data signal provided bythe data driver 500 to the data line Dj for the displaying period forperforming a displaying operation in the organic tight emitting device.

FIG. 6 shows signal timing during a sensing period in an organic lightemitting device according. to an embodiment. It is assumed in FIG. 6that the switching elements shown in FIG. 5 are p-channel electric fieldeffect transistors.

Referring to FIG. 5 and FIG. 6, during the sensing period, the switchingelement DE is turned on in response to the low-level switching controlsignal SDE, and the data driver 500 applies a sensing signal to the dataline D. A low-level scan signal SCANi is applied to the scan line Si,and the transistor Qs is turned on in response to the low-level scansignal SCANi. Therefore, the voltage corresponding to the sensing signalis stored in the capacitor Cst, and the driving transistor Qd outputs acurrent by the voltage stored in the capacitor Cst. Here, when a touchis generated, the voltage corresponding to the sensing signal is storedin the touch sensing. capacitor Cto. That is the voltage correspondingto the sensing signal is applied to the anode of the organic lightemitting element LD. When there is no touch, no touch sensing. capacitorCto is formed and the voltage corresponding to the sensing signal is notcharged into the anode.

The scan signal SCANi is switched to a high level and the switchingcontrol signal SDE is switched to a high level. The switching controlsignals SSE, SRST and SCD1 are switched to a low level. The switchingelement SE is turned on to connect the data line Dj and the sensor 710.The switching element RST is turned on to connect the second inputterminal and the output terminal of the operational amplifier 711 toallow the operational amplifier 711 to function as the unit gainoperational amplifier. The output terminal of the operational amplifier711 and the capacitor Cs1 are connected. Therefore, the voltage chargedin the capacitor Cs1 is reset by the operational amplifier 711, and anoise component existing in the data line Dj may be charged in thecapacitor Cs1.

The switching control SRST is switched to the high level to turn off theswitching element RST, and the sensing control signal SCAN_SENi providedthrough the sensing scan line SEi is switched to the low level to turnon the sensing transistor Qe. When a touch is generated, a current issupplied to the operational amplifier 711 through the data line Dj fromthe touch sensing capacitor Cto by the voltage charged in the touchsensing capacitor Ctn. In this instance since the switching element RSTis turned off, the operational amplifier 711 works as a comparator andcharges the voltage that corresponds to a comparison result of thevoltage charged in the touch sensing capacitor Cto and a referencevoltage Vset into the capacitor Cs1. That is, the sensing signalprocessor 700 measures the voltage charged in the touch sensingcapacitor Cto through the data line Dj.

The sensing control signal SCAN_SENi and the switching control signalSCD1 are switched to the high level and the switching control signals(SRST and SCD2) are switched to the low level. Therefore, the switchingelement RST is turned on to allow the operational amplifier 711 tofunction as the unit gain operational amplifier and connect an outputterminal of the operational amplifier 711 to the capacitor Cs2. Thevoltage charged in the capacitor Cs1 is reset by the operationalamplifier 711, and the noise component existing in the data line Dj ischarged in the capacitor Cs2. That is, the sensing signal processor 700measures the voltage at the data line Dj.

The sensing signal processor 700 determines a touching state through adifference between the voltage stored in the capacitor Cs1 and thevoltage stored in the capacitor Cs2. When the noise component existingin the data line Dj is stored in the capacitor Cs1, the same noisecomponent is stored in the capacitor Cs2 and the noise component isremoved through the difference of voltages stored in the capacitors Cs1and Cs2. Hence, the sensing signal processor 700 may accuratelydetermine the sensing without being influenced by the noise component.

FIG. 7, FIG. 9, FIG. 10, FIG. 11, FIG. 12, FIG. 13, and FIG. 14 areequivalent circuit diagrams of one pixel of an organic light emittingdevice according to various embodiments, FIG. 8 shows signal timing.during a sensing period in an organic light emitting device includingone pixel shown in FIG. 7, and FIG. 15 shows one frame of an organiclight emitting device according to another embodiment. FIG. 11exemplifies a pixel and a sensor connected to it.

In an embodiment, as shown in FIG. 7, a touch electrode (not shown) isconnected to the second input/output terminal of the sensing transistorQe, and the touch electrode forms a touch sensing capacitor Cto1 with anexternal touch on the rear substrate as another electrode. A bufferlayer (not shown) formed between the touch electrode and the rearsubstrate may function as a dielectric layer.

Referring to FIG. 7 and FIG. 8, differing from the signal timing shownin FIG. 6, while the switching control signal SDE has the low level andthe sensing signal is transmitted from the data line Dj, the sensingcontrol signal SCAN_SENi provided from the sensing scan line SENi isswitched to the low level. The sensing transistor Qe is turned on andthe touch sensing capacitor Cto1 charges the sensing signal transmittedthrough the data line Dj. When the sensing transistor Qe is turned onagain, the voltage charged in the touch sensing capacitor Cto2 istransmitted to the sensor 710 and is then charged in the capacitor Cs1.

In another embodiment, as shown in FIG. 9, when a touch electrode (notshown) connected to the second input/output terminal of the sensingtransistor Qe forms an electrode of the touch sensing capacitor Cto1 acapacitor Cm may be formed between the touch electrode and the anode ofthe organic light emitting element LD. A parasitic capacitance componentformed by overlapping wires may be reduced by the capacitor Cm.

In another embodiment, as shown in FIG. 10, a touch electrode (notshown) is connected to the control terminal of the driving transistorQd, and the touch electrode forms a touch sensing capacitor Cto2 with anexternal touch on the rear substrate as another electrode. A bufferlayer (not shown) formed between the touch electrode and the rearsubstrate may function as a dielectric layer. The touch sensingcapacitor Cto2 charges the sensing signal applied to the controlterminal of the driving transistor Qd, and a voltage of the controlterminal of the driving transistor Qd is determined by the voltagecharged in the touch sensing capacitor Cto2. When the sensing transistorQe is turned on, the driving transistor Qd transmits the currentcorresponding to the voltage of the control terminal to the sensor 710through the data line Dj.

The organic light emitting device including the pixel PX described withreference to FIG. 10 may be operable by the signal timing shown in FIG.6.

In another embodiment, as shown in FIG. 11, the sensing line SENj fortransmitting the sensing signal may be formed to be separated from thedata line Dj for transmitting the data signal in the pixel PX shown inFIG. 5. The display unit 100 may include a plurality of sensing linesrespectively corresponding to a plurality of sensors 710 of FIG. 4, andthe plurality of sensing lines may extend substantially in a columndirection and may be parallel with each other.

In this case, the sensing transistor Qe is connected between the sensingline SENj and the anode of the organic light emitting element LD, andthe input terminal of the sensor 710 is connected to the sensing lineSENj. Therefore, differing from the pixel PX shown in FIG. 5, theswitching elements (DE and SE) connected to the data line Dj may beomitted.

The organic light emitting device including the pixel PX exemplified inFIG. 11 may be operated with the signal timing shown in FIG. 6, exceptthat the sensing signal is applied from the sensing line SENj while thelow-level scan signal SCANi is applied from the scan line Si. In thiscase, the switch control signals (SDE and SSE) are not applied.

In another embodiment, as shown in FIG. 12, the sensing line SENj fortransmitting the sensing signal may be formed to be separated from thedata line Dj for transmitting the data signal in the pixel PX shown inFIG. 7.

In another embodiment, as shown in FIG. 13, the sensing line SENj fortransmitting the sensing signal may be formed to be separated from thedata line Dj for transmitting the data signal in the pixel PX shown inFIG. 9.

In another embodiment, as shown in FIG. 14, the sensing line SENj fortransmitting the sensing signal may be formed to be separated from thedata line Dj for transmitting the data signal in the pixel PX shown inFIG. 10.

Referring to FIG. 14, the sensing line SENj is separated from the dataline Dj so the sensing signal transmitted through the sensing line SENjdoes not influence the data signal of the data line Dj. The secondinput/output terminal of the sensing transistor Qe is separated from theterminals of the driving transistor Qd and the organic light emittingelement LD so the sensing signal transmitted through the sensing lineSENj does not influence the driving transistor Qd and the organic tightemitting element LD.

Therefore, the organic light emitting device including the pixel PXshown in FIG. 14 may perform the operation of the touch sensing periodduring the displaying period as shown in FIG. 15. That is, the organiclight emitting device may perform the display operation and sense anexternal touch.

FIG. 16 and FIG. 17 show equivalent circuit diagrams of a sensing regionof an organic light emitting device according to various embodiments.

Referring to FIG. 16 and FIG. 17, to increase capacitance of the touchsensing capacitor, touch sensing capacitors of a plurality of pixels PXmay be coupled in parallel. In this case, a plurality of pixel bunchesarranged in the row direction form a sensing region.

For example, regarding the pixel PX shown in FIG. 11, as shown in FIG.16, the sensing transistor Qe may be connected between the sensing tineSENj and the anode of the organic light emitting element LD in one pixelPX, and the sensing transistor Qe may be connected between an anode ofan organic light emitting element LD of a neighboring pixel and theanode of the present organic light emitting element LD in another pixelPX. Therefore, when the sensing transistor Qe is turned on, touchsensing transistors Cto of a plurality of pixels PX may be coupled inparallel.

Differing from this, as shown in FIG. 17, the sensing transistor Qe maybe connected between one sensing line SENj and the anode of the presentorganic light emitting element LD in the pixels PX to be coupled inparallel.

A detailed configuration of an organic tight emitting device accordingto various embodiments will now be described with reference to FIG. 18to FIG. 25.

FIG. 18 and FIG. 19 show cross-sectional views of an example of onepixel of an organic light emitting device shown in FIG. 2. FIG. 20 showsa cross-sectional view of an example of one pixel of an organic lightemitting device shown in FIG. 7. FIG. 21 shows a cross-sectional view ofan example of one pixel of an organic light emitting device shown inFIG. 9. FIG. 22 shows a cross-sectional view of an example of one pixelof an organic light emitting device shown in FIG. 10. FIG. 23 and FIG.24 show cross-sectional views of another example of one pixel of anorganic light emitting device shown in FIG. 7. FIG. 25 shows across-sectional view of another example of one pixel of an organic lightemitting device shown in FIG. 2. The organic light emitting deviceaccording to an embodiment is a bottom emission type, so FIG. 18, FIG.19, FIG. 20, FIG. 21, FIG. 22, FIG. 23, FIG. 24, and FIG. 25 show thatthe rear side is provided upward, for convenience. Further, FIG. 18,FIG. 19, FIG. 20, FIG. 21, FIG. 22, FIG. 23, FIG. 24, and FIG. 25 do notillustrate all of switching elements and wires.

Referring to FIG. 18, a buffer layer 111 is provided on a rear substrate110 that is an insulation substrate made of transparent glass orplastic. The buffer layer 111 may prevent permeation of impurities, andits surface may be flat. The buffer layer 111 may include a siliconnitride (SiNx), a silicon oxide (SiOx), or a silicon oxynitride(SiOxNy). The buffer layer 111 may be omitted.

A first semiconductor layer 154 a and a second semiconductor layer 154 bare formed on the buffer layer 111. The first semiconductor layer 154 amay include a channel region 152 a, and a source region (not shown) anda drain region (not shown) provided on respective sides of the channelregion 152 a and formed through doping.

The second semiconductor layer 154 b may include a channel region 152 band a source region 153 b and drain region 155 b provided on respectivesides of the channel region 152 b and formed through doping. The sourceregion 153 b and the drain region 155 b are operable as a firstinput/output terminal and a second input/output terminal of the drivingtransistor (Qd of FIG. 2), for example, of the driving element. Thefirst semiconductor layer 154 a and the second semiconductor layer 154 bmay include an amorphous silicon, a polysilicon, or an oxidesemiconductor.

A gate insulating layer 140 made of a silicon nitride (SiNx) or asilicon oxide (SiOx) is provided on the first semiconductor layer 154 aand the second semiconductor layer 154 b.

For example, a plurality of gate conductors including a first gateelectrode 124 a operable as a control terminal of the switchingtransistor Qs and a second gate electrode 124 b operable as a controlterminal of the driving transistor Qd are formed on the gate insulatinglayer 140. The first gate electrode 124 a may overlap part of the firstsemiconductor layer 154 a, particularly the channel region 152 a, andthe second gate electrode 124 b may overlap part of the secondsemiconductor layer 154 b, particularly the channel region 152 b.

A first passivation layer 180 a is provided on the gate insulating layer140 and the gate conductor. The first passivation layer 180 a and thegate insulating layer 140 include a contact hole 183 b extending to andfor exposing the source region 153 b of the second semiconductor layer154 b, and a contact hole 185 b extending to and for exposing the drainregion 155 b. The first passivation layer 180 a may further include acontact hole (not shown) for exposing a source region (not shown) and adrain region not shown) of the first semiconductor layer 154 a.

A plurality of data conductors including a data line (not shown), adriving voltage tine (not shown), and a plurality of input and outputelectrodes 173 b and 175 b are formed on the first passivation layer 180a.

The first input and output electrode 173 b and the second input andoutput electrode 175 b may be islands separable from each other, and maybe connected to the source region 153 b and the drain region 1556 of thesecond semiconductor layer 1546 through the contact holes 183 b and 185b. The first input and output electrode 173 b may be formed to be partof a driving voltage line for transmitting a driving voltage.

A second passivation layer 180 b made of an inorganic insulator such asa silicon nitride or a silicon oxide may be provided on the dataconductor. The second passivation layer 180 b may remove steps and mayhave a flat surface to increase an emission efficiency of the organiclight emitting element to be formed thereon. The second passivationlayer 180 b may have a contact hole extending to and for exposing thesecond input and output electrode 175 b.

A pixel electrode 191 is provided on the second passivation layer 180 b.The pixel electrode 191 may include a semi-transmissible ortransmittable material.

The pixel electrode 191 of the pixel PX is physically and electricallyconnected to the second input and output electrode 175 b through thecontact hole of the second passivation layer 180 b.

A pixel defining layer (also called a partition) 360 with an openingextending to and for exposing the pixel electrode 191 may be provided onthe second passivation layer 180 b. The opening of the pixel defininglayer 360 may define the pixel area.

An emission member 370 is provided on the pixel defining layer 360 andthe pixel electrode 191. The emission member 370 may include a firstorganic common layer (not shown), an emission layer (not shown), and asecond organic common layer (not shown) that are stacked sequentially.

The first organic common layer may exemplarily include at least one of ahole injecting layer and a hole transport layer that are stackedsequentially. The first organic common layer may be formed all over thedisplay area in which the pixels PX are disposed, or may be formed ineach pixel area.

The emission layer may be provided on the pixel electrode 191 of thecorresponding pixel PX. The emission layer may be made of an organicmaterial which uniquely emits light of primary colors such as red,green, and blue, and may have a structure in which a plurality oforganic material layers emitting light of different colors arelaminated. For example, a red organic emission layer may be deposited onthe first organic common layer of the pixel PX representing red, a greenorganic emission layer may be deposited on the first organic commonlayer of the pixel PX representing green, and a blue organic emissionlayer may be deposited on the first organic common layer of the pixel PXrepresenting blue. However, it is not limited thereto, and an organicemission layer representing one primary color may be deposited in thepixel PX representing the different colors. According to anotherembodiment, the emission layer may include a white emission layerexpressing white.

For example, the second organic common layer may include at least one ofthe electron transport layer (ETL) and the electron injection layer(EIL) that are sequentially deposited. The second organic common layermay be formed throughout the entire display area where the pixel PX isdisposed, or may be formed in the region of each pixel PX.

The first and second organic common layers improve the luminousefficiency of the emission layer, and one of the first and secondorganic common layers may be omitted.

A common electrode 270 for transmitting a common voltage ELVSS is formedon the emission member 370. The common electrode 270 may include areflective material. For example, the common electrode 270 is made ofthe transparent conductive material or is formed by thinly depositing ametal such as calcium (Ca), barium (Ba), magnesium (Mg), aluminum (Al),and silver (Ag) to allow light transmittance.

The pixel electrode 191, the light emitting member 370, and the commonelectrode 270 of each pixel PX form the organic light emitting elementLD, previously described, and one of the pixel electrode 191 and thecommon electrode 270 may be a cathode, while the other may be an anode.

A touch electrode 112 is formed between the rear substrate 110 and thebuffer layer 111. The touch electrode 112 may include a transparentconductive material.

In this case, the touch electrode 112 may be extended to a regioncorresponding to the emission member 370 of the pixel PX. The bufferlayer 111, the gate insulating layer 140, and the first passivationlayer 180 a have a contact hole 187 a extending to and for exposing thetouch electrode 112. A connection electrode 177 is formed in the contacthole 187 a as an island. The pixel electrode 191 is connected to theconnection electrode 177 through a contact hole 187 b formed in thesecond passivation layer 180 b so the touch electrode 112 is connectedto the pixel electrode 191.

Therefore, the pixel electrode 191, that is, the touch electrode 112connected to the anode of the organic light emitting element LD, mayfunction as an electrode of the touch sensing capacitor Cto shown inFIG. 2.

In another embodiment, as shown in FIG. 19, a touch electrode 112 a maybe formed throughout the display area to expose the region thatcorresponds to the emission member 370 of the pixel PX. In this case,the touch electrode 112 a may include a reflective conductive material.The touch electrode 112 a may then function as an electrode of the touchsensing capacitor Cto shown in FIG. 5, and may reduce reflectance of theorganic light emitting device.

In another embodiment, as shown in FIG. 20, a third semiconductor layer154 c is formed on the buffer layer 111. The third semiconductor layer154 c may include a channel region 152 c and a source region 153 c anddrain region 155 c provided on respective sides of the channel region152 c and formed through doping. The source region 153 c and the drainregion 155 c are exemplarily operable as a first input/output terminaland a second input/output terminal of the sensing transistor (Qe of FIG.2).

A third gate electrode 124 c that is operable as a control terminal ofthe sensing transistor Qe is formed on the gate insulating layer 140.The third gate electrode 124 c may overlap part of the thirdsemiconductor layer 154 c, particularly the channel region 152 c.

The first passivation layer 180 a and the gate insulating layer 140further include a contact hole 183 c for exposing the source region 153c of the third semiconductor layer 154 c and a contact hole 185 c forexposing the drain region 155 c.

A first input and output electrode 173 c and a second input and outputelectrode 175 c that are separable from each other are formed on thefirst passivation layer 180 a. The first input and output electrode 173c and the second input and output electrode 175 c may be connected tothe source region 153 c and the drain region 155 c of the thirdsemiconductor layer 154 c through the contact holes 183 c and 185 c. Thefirst input and output electrode 173 c may be connected to the data lineor the sensing line.

Here, a partial region of the third semiconductor layer 154 c, forexample, the drain region 155 c, may extend to the region correspondingto the emission member 370 and form a touch electrode of the pixel PXshown in FIG. 7.

In another embodiment, as shown in FIG. 21, an auxiliary electrode 193is further provided on the second passivation layer 180 b. The auxiliaryelectrode 193 is separated from the pixel electrode 191, and isconnected to the second input and output electrode 175 c through acontact hole 187 c of the second passivation layer 180 b. Therefore, thepixel electrode 191 and the auxiliary electrode 193 may form thecapacitor Cm shown in FIG. 9.

In another embodiment, as shown in FIG. 22, the gate electrodes 124 aand 124 b may be formed with two layers. A gate conductor made of atransparent conductive material may be formed on the gate insulatinglayer 140, and gate electrodes 124 a and 124 b may be formed on the gateconductor made of a transparent conductive material. When thedouble-layered gate electrodes are formed as described, parts 125 a, 125b, and 125 c of the gate conductor of a transparent conductive materialmay remain through selective etching. In this instance, the gateconductor 125 c in the region corresponding to the emission member 370is formed to be connected to the gate electrode 124 b formed on thesecond semiconductor layer 154 b. The gate conductor 125 c may thenfunction as an electrode of the touch sensing capacitor Cto2 shown inFIG. 10.

In the other embodiment, a gate self-alignment configuration may be usedas shown in FIG. 23. The first semiconductor layer 154 a, the secondsemiconductor layer 154 b, and the third semiconductor layer 154 c mayinclude an oxide semiconductor. In this case, the gate insulating layers140 a, 104 b, and 140 c may be formed in the channel regions 152 a, 152b, and 152 c of the semiconductor layers 154 a, 154 b, and 154 c throughselective etching. A partial region of the third semiconductor layer 154c, for example, the drain region 155 c may extend to the regioncorresponding to the emission member 370 to form a touch electrode ofthe pixel PX shown in FIG. 7.

In another embodiment, as shown in FIG. 24 and FIG. 25, the gateelectrodes 124 a, 124 b, and 124 c may be formed below the semiconductorlayers 154 a, 154 b, and 154 c.

Referring to FIG. 24, a gate conductor including gate electrodes 124 a,124 b, and 124 c is formed on the buffer layer 111 and the gateinsulating layer 140 covers the gate conductor. The first semiconductorlayer 154 a, the second semiconductor layer 154 b, and the thirdsemiconductor layer 154 c are formed on the gate insulating layer 140.The first semiconductor layer 154 a, the second semiconductor layer 154b and the third semiconductor layer 154 c may include an oxidesemiconductor. The first gate electrode 124 a may overlap part of thefirst semiconductor layer 154 a, the second gate electrode 124 b mayoverlap part of the second semiconductor layer 154 b and the third gateelectrode 124 c may overlap part of the third semiconductor layer 154 c.

An etch stopper (also called an etching preventing layer) 130 a isprovided in the channel region 152 a of the first semiconductor layer154 a, an etch stopper 130 b is provided in the channel region 152 b ofthe second semiconductor layer 154 b, and an etch stopper 130 c isprovided in the channel region 152 c of the third semiconductor layer154 c. In this instance, right and left edge borders of the etchstoppers 130 a, 130 b, and 130 c may be substantially arranged tocorrespond to right and left edge borders of the channel regions 152 a,152 b, and 152 c. Therefore, the etch stoppers 130 a, 130 b, and 130 cmay not substantially overlap the source region or the drain region.

The first passivation layer 180 a covers the etch stoppers 130 a, 130 band 130 c. The etch stoppers 130 a, 130 b, and 130 c cover the channelregions 152 a, 152 b, and 152 c to prevent the channel regions 152 a,152 b, and 152 c from being damaged by an etchant. The etch stoppers 130a, 130 b and 130 c prevent diffusion of impurities to the channelregions 152 a, 152 b, and 152 c from an insulating layer such as thefirst passivation layer 180 a or the outside to prevent a change ofproperties of the channel regions 152 a, 152 b, and 152 c.

The etch stoppers 130 a, 130 b, and 130 c may be formed of an inorganiclayer including at least one material of SiOx SiNx, SiOCx, and SiONx, oran organic layer including an organic material or a polymer organicmaterial.

In this instance, a partial region of the third semiconductor layer 154c, for example, the drain region 155 c, extends to the regioncorresponding to the emission member 370 to form a touch electrode ofthe pixel PX shown in FIG. 7.

Referring to FIG. 25, differing from FIG. 24, the etch stopper 130covers the first and second semiconductor layers 154 a and 154 b and thegate insulating layer 140 on which the semiconductor layers 154 a and154 b are not formed. The etch stopper 130 includes a contact hole 183 bfor exposing the source region 153 b of the second semiconductor layer154 b and a contact hole 1.85 b for exposing the drain region 155 b. Theetch stopper 130 may further include a contact hole (not shown) forexposing a source region (not shown) and a drain region (not shown) ofthe first semiconductor layer 154 a. The first passivation layer (notshown) may cover the etch stopper 130.

A touch electrode 124 d is formed on the same layer as the gateconductor. The touch electrode 124 d may include a transparentconductive material. In this case, the touch electrode 124 d may beextended to the region corresponding to the emission member 370 of thepixel PX. The gate insulating layer 140 and the second passivation layer180 b have a contact hole 189 for exposing the touch electrode 124 d.The pixel electrode 191 is connected to the touch electrode 124 dthrough the contact hole 189.

Therefore, the pixel electrode 191, that is, the touch electrode 124 dconnected to the anode of the organic light emitting element LD, mayfunction as an electrode of the touch sensing capacitor Cto shown inFIG. 2, thereby providing the touch sensing function without increasingthe thickness or the weight of the organic light emitting deviceaccording to the various embodiments.

While this disclosure has been described in connection with what ispresently considered to be practical embodiments, it is to be understoodthat the inventive concept is not limited to the disclosed embodiments,but on the contrary, is intended to cover various modifications andequivalent arrangements included within the spirit and scope of theappended claims.

What is claimed is:
 1. A display device comprising: a rear substrate; adriving element disposed on the rear substrate; a passivation layercovering the driving element; a pixel electrode disposed on thepassivation layer and connected to the driving element; an organicemission layer disposed on the pixel electrode and configured to emitlight toward the rear substrate; a common electrode disposed on theorganic emission layer; and a touch electrode disposed between the rearsubstrate and the passivation layer and configured to form a capacitancecomponent when a touch is generated.
 2. The display device of claim 1,wherein the touch electrode is connected to the pixel electrode.
 3. Thedisplay device of claim 2, further comprising a buffer layer disposedbetween the rear substrate and the driving element, wherein the touchelectrode is disposed between the rear substrate and the buffer layer.4. The display device of claim 2, wherein the touch electrode covers theorganic emission layer and includes a transparent conductive material.5. The display device of claim 2, wherein the touch electrode exposesthe organic emission layer and includes a reflective conductivematerial.
 6. The display device of claim 1, wherein the touch electrodeis disposed on a same layer as a semiconductor layer of the drivingelement and includes a semiconductor material.
 7. The display device ofclaim 6, further comprising a sensing element disposed on a same layeras the driving element and configured to transmit a sensing signal forsensing a touch. wherein the touch electrode is connected to the sensingelement.
 8. The display device of claim 6, further comprising anauxiliary electrode disposed on a same layer as the pixel electrode andseparated from the pixel electrode. wherein the auxiliary electrode isconnected to the touch electrode.
 9. The display device of claim 1,wherein the driving element includes a first gate electrode and a secondgate electrode disposed on the first gate electrode, and the touchelectrode is disposed on a same layer as the first gate electrode. 10.The display device of claim 9, wherein the touch electrode includes atransparent conductive material.
 11. A display device comprising: atleast one signal line configured to transmit a data signal and a sensingsignal; a scan line configured to transmit a scan signal; a pixelincluding a touch electrode configured to store a voltage correspondingto the sensing signal for a first period when an external touch occurs,and disposed in a region defined by the signal line and the scan line;and a sensing signal processor configured to measure a voltage stored inthe touch electrode through the signal tine for a second period afterthe first period, to measure a voltage of the signal line for a thirdperiod after the second period, and to sense the external touch basedupon a difference between the voltage measured for the second period andthe voltage measured for the third period.
 12. The display device ofclaim 11, wherein the pixel further includes: a switching transistorconfigured to transmit the data signal in response to the scan signal; acapacitor configured to store a voltage corresponding to the data signalfrom the switching transistor; a driving transistor configured to outputa current caused by the voltage stored in the capacitor; and an organiclight emitting element configured to emit light according. to thecurrent from the driving. transistor.
 13. The display device of claim12, wherein the touch electrode is connected to a first terminal of theorganic light emitting element.
 14. The display device of claim 12,wherein the touch electrode is connected to a gate electrode of thedriving transistor.
 15. The display device of claim 12, furthercomprising a sensing transistor configured to be turned on for the firstperiod to transmit a voltage stored in the touch electrode to the signalline.
 16. The display device of claim 15, wherein the sensing transistorincludes a first input/output terminal connected to the signal line anda second input/output terminal connected to the touch electrode.
 17. Thedisplay device of claim 11, wherein the signal line includes a data lineconfigured to transmit the data signal and a sensing line configured totransmit the sensing signal.
 18. The display device of claim 11, whereinthe signal line includes a data line configured to transmit the datasignal for a displaying period and to transmit the sensing signal for atouch sensing period, and the touch sensing period includes the firstperiod, the second period, and the third period.
 19. The display deviceof claim 11, wherein the sensing signal processor includes: anoperational amplifier including a first input terminal connected to thesignal line, a second input terminal for receiving a reference voltage,and an output terminal; a first capacitor; a second capacitor; a firstswitching element connected between the output terminal and the firstcapacitor and configured to be turned on for the second period; and asecond switching element connected between the output terminal and thesecond capacitor and configured to be turned on for the third period.20. A touch sensing method by a display device including at least onesignal line for transmitting a data signal and a sensing signal, a scanline for transmitting a scan signal, and a pixel disposed in a regiondefined by the signal line and the scan line and including a touchelectrode, comprising: storing a voltage corresponding to the sensingsignal in the touch electrode for a first period when an external touchoccurs; measuring the voltage stored in the touch electrode through thesignal tine for a second period after the first period; measuring thevoltage at the signal line for a third period after the second period;and sensing the external touch based upon a difference between thevoltage measured for the second period and the voltage measured for thethird period.